Validate inputs using while loop

Question

I am trying to do a simple program that validates and allocates grades to a student based on the scores input using both a while loop and a do-while loop. I understand this is simple, the code works fine without validating, but the loops don't loop and program is terminated. This is what I've got so far

import io.*;
public class Marks {
    public static void main(String[] args) {
        double marks, inMarks;
        int assess, inAssess, calcMark, ten;
        boolean dna, dnc, fail, pass, calcDna, calcDnc, calcF, calcP;
        marks = inMarks();
        assess = inAssess();
        dna = calcDna(assess);
        dnc = calcDnc(assess);
        fail = calcF(assess, marks);
        pass = calcP(assess, marks);
        ten = calcMark(marks);

        if (dna == false) {
            if (dnc == true) {
                System.out.println("DNC-" + (int) marks);
            } else if (fail == true) {
                System.out.println("F-" + (int) marks);
            } else if (pass == true) {
                System.out.println(ten + "-" + (int) marks);
            }
        } else {
            System.out.println("DNA");
        }
    }
    private static double inMarks() {
        double marks;
        boolean validMark;
        marks = ConsoleInput.readDouble("Input student's mark");
        while ((marks < 0) && (marks > 100)) {
            System.out.println("invalid mark, please enter again");
            marks = ConsoleInput.readDouble("Input student's mark");
        }
        // Assertion 0 > marks > 100
        return marks;
    }

    private static int inAssess() {
        int assess;
        boolean validAssess;
        do {
            assess = ConsoleInput
                    .readInt("Input number of assessments student completed");
            if ((0 > assess) && (assess > 5)) {
                System.out
                        .println("invalid assessment attendence. please enter again");
            }
        } while ((0 >= assess) && (assess >= 5));
        // Assertion 0 < assess < 5
        return assess;
    }
    private static boolean calcDna(int assess) {
        boolean calcDna;
        calcDna = false;
        if ((assess == 0)) {
            calcDna = true;
        }
        return calcDna;
    }

    private static boolean calcDnc(int assess) {
        boolean calcDnc;
        calcDnc = false;
        if ((assess > 0) && (assess <= 4)) {
            calcDnc = true;
        }
        return calcDnc;
    }

    private static boolean calcF(int assess, double marks) {
        boolean calcF;
        calcF = false;
        if ((assess == 5) && (marks < 50.0)) {
            calcF = true;
        }
        return calcF;
    }

    private static boolean calcP(int assess, double marks) {
        boolean calcP;
        calcP = false;
        if ((assess == 5) && (marks > 50.0)) {
            calcP = true;
        }
        return calcP;
    }

    private static int calcMark(double marks) {
        int ten;
        ten = (int) marks / 10;
        return ten;

    }
}

Which loops are you referring to? Can you highlight the ones not working in the code. — Nikhil
– Nikhil, Commented Sep 30, 2013 at 17:37
@Rohit Jain the loops are in the methods inMarks and inAssess. — CPerkins
– CPerkins, Commented Sep 30, 2013 at 17:40

hasan · Accepted Answer · 2013-09-30 17:54:21Z

2

First problem:

while( (marks < 0) && (marks > 100))

Must be or:

while( (marks < 0) || (marks > 100))

No number exists is less than 0 and larger than 100 :)

do {
    assess = ConsoleInput.readInt ("Input number of assessments student completed");
    if((0 <= assess ) || (assess >= 5))
    {
        System.out.println("invalid assessment attendence. please enter again");
    }
} while ((0 <= assess) || ( assess >= 5));

edited Sep 30, 2013 at 17:54

answered Sep 30, 2013 at 17:37

hasan

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3 Comments

Ryane Over a year ago

this solves the problem with the inMarks but if i did the same with inAssess it infinitely loops if assess input is 5 or 0

Ryane Over a year ago

i've got not enough rep sorry :S

BartoszKP Over a year ago

@hasan Ryane's edit was correct, but it was rejected as a too radical change of your original post. Please fix the code yourself - you've inverted the conditions. It is a good habit to test your code before you post it as a solution.

CPerkins · Accepted Answer · 2013-09-30 17:37:36Z

2

If by "the loops dont loop", you're referring to this:

while( (marks < 0) && (marks > 100))

then your problem is that marks cannot possibly be both less than zero and greater than 100.

Comments

Ryane · Accepted Answer · 2013-09-30 17:57:24Z

1

changed

while( (marks < 0) && (marks > 100));

while ((0 >= assess) && ( assess >= 5));

to

while( (marks < 0) || (marks > 100))

while ((0 > assess) && ( assess > 5));

answered Sep 30, 2013 at 17:57

Ryane

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